The unstoppable George Takei has gone from minor "Star Trek" stardom to online and pop-culture phenomenon, with 428,000 Twitter followers, 2.5 million Facebook likes and guest gigs on everything from "The Howard Stern Show" to "The Apprentice."

At the Old Globe Theatre on Thursday, though, he was just another actor -- part of a sprawling ensemble working through scenes from the new musical "Allegiance" at the theater's cavernous subterranean rehearsal complex in Balboa Park.

That is, until he let out a laugh or two. No one's sounds quite like the baritone-voiced Takei's.

The L.A.-born actor was the inspiration behind the potentially Broadway-bound "Allegiance," a show whose historical backdrop is the internment of Japanese-Americans during World War II.

Takei's own family was among those sent to relocation camps in that era, and his chance meeting many decades later with composer-writer Jay Kuo and writer-producer Lorenzo Thione is what led to the musical's inception. (The pair is now working with a third writer, Marc Acito of the Globe's recent "A Room With a View.")

I joined U-T photographer Ed Contreras to catch up with the "Allegiance" team yesterday (we'll have a full preview piece in the Sunday Arts section soon), and watched Takei and fellow cast members -- including the Tony-winning Lea Salonga ("Miss Saigon") and rising Broadway and "Glee" star Telly Leung -- run through a key early scene under the direction of Globe returnee Stafford Arima.

The action involved a group of internees being checked into the camp by some highly unsympathetic guards. (Two of them are played by Geno Carr and Kurt Norby, a couple of distinguished San Diego actors whose presence in the cast, along with that of fellow local Brandon Joel Maier, is a welcome nod to the talent being developed at our smaller theaters.)

Given that it's still early in rehearsals, there were a few fits and starts - and one pause as Takei struggled to get a balky suitcase open, which prompted the first laugh.

"Allegiance," of course, is not a comedy. But the sly Mr. Takei has a way of bringing some levity anyway.